Mg粉添加量对泡沫铝发泡行为的影响

Effect of addition of Mg powders on foaming behaviors of Al foams

利用粉末冶金法制备不同Mg粉添加量的纯铝闭孔泡沫铝材料,并对Mg粉添加量对泡沫铝发泡行为及泡沫稳定性的影响进行研究。结果表明:Mg粉的添加导致前驱体膨胀率的显著增大和泡沫体泡孔结构的均匀化;添加的Mg粉同空气雾化Al粉表面的Al2O3反应,生成同铝熔体有良好润湿性的MgAl2O4相,打破原有铝粉表面的氧化物结构,生成的MgAl2O4相均匀地分布于泡孔的布拉德边界和泡壁上;润湿性MgAl2O4相的出现增加熔体的表观黏度,大大减弱重力排液、毛细作用和气泡流动带来的负面影响,从而提高泡沫的稳定性;在空气雾化工业纯Al粉含氧量(质量分数)为(0.34±0.01)%和Mg粉添加量为(0.6%～1.0)%的条件下,可以获得最佳的膨胀率和均匀的泡孔结构。

Closed-cell pure aluminum （Al） foams with Mg powders were prepared by powder metallurgy route. The effects of addition of Mg powders on the foaming behaviors and foam stability were discussed. The results show that the expansion rate of the precursor increases significantly with addition of Mg powders and uniform cell structures of Al foams are obtained; MgAl2O4 phases with good wettability with Al melt are formed due to the reaction between Mg powders and Al2O3 on the surface of Al powders; original oxide structures on surfaces of Al powder are destroyed and MgAl2O4 phases locate uniformly into the plateau borders and cell walls; the apparent viscosity of melt is enhanced due to the present of MgAl2O4 phases. Negative impacts caused by gravity drainage,capillarity and bubble flow are weakened greatly and hence foam stability is improved. The optimum expansion rate and uniform cell structures are achieved as oxygen content for air-atomized Al powder is （0.34±0.01）% （mass fraction） and addition of Mg powder is （0.6%～1.0） %.